1. Field of the Invention
The present invention relates to a substrate used for epitaxially growing an electro-optical single crystal thin film made of BaTiO3 (BTO: barium titanate), PbTiO3, BiKTiO3 etc., used for an optical switch, an optical modulator, etc., and a method of manufacturing the same.
2. Description of the Related Art
A BTO single crystal is a transparent crystal made of Ba (barium), Ti (titanium), and O (oxygen), and is known as a material that provides a very large secondary electro-optical effect (Kerr effect) which determines an efficiency of an optical device.
As for the above-mentioned BTO single crystal, it is known that a BTO single crystal thin film is formed on an Si (001) (silicon, (001) face) substrate via an MgO (magnesium oxide) single crystal layer as a buffer layer for buffering lattice mismatch between Si and BTO (see J. Mater. Res., Vol.12, No.4, pp 1152-1159, April 1997).
However, in the above-mentioned BTO single crystal, the lattice mismatch between Si and BTO is not fully relieved, so that BTO is polycrystallized, making it difficult to manufacture the optical device.